vm_fault.c revision 329707
1/*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70/* 71 * Page fault handling module. 72 */ 73 74#include <sys/cdefs.h> 75__FBSDID("$FreeBSD: stable/10/sys/vm/vm_fault.c 329707 2018-02-21 11:31:29Z kib $"); 76 77#include "opt_ktrace.h" 78#include "opt_vm.h" 79 80#include <sys/param.h> 81#include <sys/systm.h> 82#include <sys/kernel.h> 83#include <sys/lock.h> 84#include <sys/proc.h> 85#include <sys/resourcevar.h> 86#include <sys/rwlock.h> 87#include <sys/sysctl.h> 88#include <sys/vmmeter.h> 89#include <sys/vnode.h> 90#ifdef KTRACE 91#include <sys/ktrace.h> 92#endif 93 94#include <vm/vm.h> 95#include <vm/vm_param.h> 96#include <vm/pmap.h> 97#include <vm/vm_map.h> 98#include <vm/vm_object.h> 99#include <vm/vm_page.h> 100#include <vm/vm_pageout.h> 101#include <vm/vm_kern.h> 102#include <vm/vm_pager.h> 103#include <vm/vm_extern.h> 104#include <vm/vm_reserv.h> 105 106#define PFBAK 4 107#define PFFOR 4 108 109static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 110 111#define VM_FAULT_READ_BEHIND 8 112#define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 113#define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) 114#define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) 115#define VM_FAULT_CACHE_BEHIND (VM_FAULT_READ_BEHIND * VM_FAULT_SUM) 116 117struct faultstate { 118 vm_page_t m; 119 vm_object_t object; 120 vm_pindex_t pindex; 121 vm_page_t first_m; 122 vm_object_t first_object; 123 vm_pindex_t first_pindex; 124 vm_map_t map; 125 vm_map_entry_t entry; 126 int lookup_still_valid; 127 int map_generation; 128 struct vnode *vp; 129}; 130 131static void vm_fault_cache_behind(const struct faultstate *fs, int distance); 132static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 133 int faultcount, int reqpage); 134 135static inline void 136release_page(struct faultstate *fs) 137{ 138 139 vm_page_xunbusy(fs->m); 140 vm_page_lock(fs->m); 141 vm_page_deactivate(fs->m); 142 vm_page_unlock(fs->m); 143 fs->m = NULL; 144} 145 146static inline void 147unlock_map(struct faultstate *fs) 148{ 149 150 if (fs->lookup_still_valid) { 151 vm_map_lookup_done(fs->map, fs->entry); 152 fs->lookup_still_valid = FALSE; 153 } 154} 155 156static void 157unlock_vp(struct faultstate *fs) 158{ 159 160 if (fs->vp != NULL) { 161 vput(fs->vp); 162 fs->vp = NULL; 163 } 164} 165 166static void 167unlock_and_deallocate(struct faultstate *fs) 168{ 169 170 vm_object_pip_wakeup(fs->object); 171 VM_OBJECT_WUNLOCK(fs->object); 172 if (fs->object != fs->first_object) { 173 VM_OBJECT_WLOCK(fs->first_object); 174 vm_page_lock(fs->first_m); 175 vm_page_free(fs->first_m); 176 vm_page_unlock(fs->first_m); 177 vm_object_pip_wakeup(fs->first_object); 178 VM_OBJECT_WUNLOCK(fs->first_object); 179 fs->first_m = NULL; 180 } 181 vm_object_deallocate(fs->first_object); 182 unlock_map(fs); 183 unlock_vp(fs); 184} 185 186static void 187vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 188 vm_prot_t fault_type, int fault_flags, bool set_wd) 189{ 190 bool need_dirty; 191 192 if (((prot & VM_PROT_WRITE) == 0 && 193 (fault_flags & VM_FAULT_DIRTY) == 0) || 194 (m->oflags & VPO_UNMANAGED) != 0) 195 return; 196 197 VM_OBJECT_ASSERT_LOCKED(m->object); 198 199 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 200 (fault_flags & VM_FAULT_WIRE) == 0) || 201 (fault_flags & VM_FAULT_DIRTY) != 0; 202 203 if (set_wd) 204 vm_object_set_writeable_dirty(m->object); 205 else 206 /* 207 * If two callers of vm_fault_dirty() with set_wd == 208 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 209 * flag set, other with flag clear, race, it is 210 * possible for the no-NOSYNC thread to see m->dirty 211 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 212 * around manipulation of VPO_NOSYNC and 213 * vm_page_dirty() call, to avoid the race and keep 214 * m->oflags consistent. 215 */ 216 vm_page_lock(m); 217 218 /* 219 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 220 * if the page is already dirty to prevent data written with 221 * the expectation of being synced from not being synced. 222 * Likewise if this entry does not request NOSYNC then make 223 * sure the page isn't marked NOSYNC. Applications sharing 224 * data should use the same flags to avoid ping ponging. 225 */ 226 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 227 if (m->dirty == 0) { 228 m->oflags |= VPO_NOSYNC; 229 } 230 } else { 231 m->oflags &= ~VPO_NOSYNC; 232 } 233 234 /* 235 * If the fault is a write, we know that this page is being 236 * written NOW so dirty it explicitly to save on 237 * pmap_is_modified() calls later. 238 * 239 * Also tell the backing pager, if any, that it should remove 240 * any swap backing since the page is now dirty. 241 */ 242 if (need_dirty) 243 vm_page_dirty(m); 244 if (!set_wd) 245 vm_page_unlock(m); 246 if (need_dirty) 247 vm_pager_page_unswapped(m); 248} 249 250static void 251vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m) 252{ 253 254 if (m_hold != NULL) { 255 *m_hold = m; 256 vm_page_lock(m); 257 vm_page_hold(m); 258 vm_page_unlock(m); 259 } 260} 261 262/* 263 * Unlocks fs.first_object and fs.map on success. 264 */ 265static int 266vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 267 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 268{ 269 vm_page_t m; 270 int rv; 271 272 MPASS(fs->vp == NULL); 273 m = vm_page_lookup(fs->first_object, fs->first_pindex); 274 /* A busy page can be mapped for read|execute access. */ 275 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 276 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 277 return (KERN_FAILURE); 278 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type | 279 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), 0); 280 if (rv != KERN_SUCCESS) 281 return (rv); 282 vm_fault_fill_hold(m_hold, m); 283 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false); 284 VM_OBJECT_RUNLOCK(fs->first_object); 285 if (!wired) 286 vm_fault_prefault(fs, vaddr, 0, 0); 287 vm_map_lookup_done(fs->map, fs->entry); 288 curthread->td_ru.ru_minflt++; 289 return (KERN_SUCCESS); 290} 291 292/* 293 * vm_fault: 294 * 295 * Handle a page fault occurring at the given address, 296 * requiring the given permissions, in the map specified. 297 * If successful, the page is inserted into the 298 * associated physical map. 299 * 300 * NOTE: the given address should be truncated to the 301 * proper page address. 302 * 303 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 304 * a standard error specifying why the fault is fatal is returned. 305 * 306 * The map in question must be referenced, and remains so. 307 * Caller may hold no locks. 308 */ 309int 310vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 311 int fault_flags) 312{ 313 struct thread *td; 314 int result; 315 316 td = curthread; 317 if ((td->td_pflags & TDP_NOFAULTING) != 0) 318 return (KERN_PROTECTION_FAILURE); 319#ifdef KTRACE 320 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 321 ktrfault(vaddr, fault_type); 322#endif 323 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 324 NULL); 325#ifdef KTRACE 326 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 327 ktrfaultend(result); 328#endif 329 return (result); 330} 331 332int 333vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 334 int fault_flags, vm_page_t *m_hold) 335{ 336 vm_prot_t prot; 337 long ahead, behind; 338 int alloc_req, era, faultcount, nera, reqpage, result; 339 boolean_t dead, is_first_object_locked, wired; 340 vm_object_t next_object; 341 vm_page_t marray[VM_FAULT_READ_MAX]; 342 int hardfault; 343 struct faultstate fs; 344 struct vnode *vp; 345 int locked, error; 346 347 hardfault = 0; 348 PCPU_INC(cnt.v_vm_faults); 349 fs.vp = NULL; 350 faultcount = reqpage = 0; 351 352RetryFault:; 353 354 /* 355 * Find the backing store object and offset into it to begin the 356 * search. 357 */ 358 fs.map = map; 359 result = vm_map_lookup(&fs.map, vaddr, fault_type | 360 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object, 361 &fs.first_pindex, &prot, &wired); 362 if (result != KERN_SUCCESS) { 363 unlock_vp(&fs); 364 return (result); 365 } 366 367 fs.map_generation = fs.map->timestamp; 368 369 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 370 panic("vm_fault: fault on nofault entry, addr: %lx", 371 (u_long)vaddr); 372 } 373 374 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 375 fs.entry->wiring_thread != curthread) { 376 vm_map_unlock_read(fs.map); 377 vm_map_lock(fs.map); 378 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 379 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 380 unlock_vp(&fs); 381 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 382 vm_map_unlock_and_wait(fs.map, 0); 383 } else 384 vm_map_unlock(fs.map); 385 goto RetryFault; 386 } 387 388 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0); 389 390 if (wired) 391 fault_type = prot | (fault_type & VM_PROT_COPY); 392 else 393 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 394 ("!wired && VM_FAULT_WIRE")); 395 396 /* 397 * Try to avoid lock contention on the top-level object through 398 * special-case handling of some types of page faults, specifically, 399 * those that are both (1) mapping an existing page from the top- 400 * level object and (2) not having to mark that object as containing 401 * dirty pages. Under these conditions, a read lock on the top-level 402 * object suffices, allowing multiple page faults of a similar type to 403 * run in parallel on the same top-level object. 404 */ 405 if (fs.vp == NULL /* avoid locked vnode leak */ && 406 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 407 /* avoid calling vm_object_set_writeable_dirty() */ 408 ((prot & VM_PROT_WRITE) == 0 || 409 (fs.first_object->type != OBJT_VNODE && 410 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 411 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 412 VM_OBJECT_RLOCK(fs.first_object); 413 if ((prot & VM_PROT_WRITE) == 0 || 414 (fs.first_object->type != OBJT_VNODE && 415 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 416 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) { 417 result = vm_fault_soft_fast(&fs, vaddr, prot, 418 fault_type, fault_flags, wired, m_hold); 419 if (result == KERN_SUCCESS) 420 return (result); 421 } 422 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 423 VM_OBJECT_RUNLOCK(fs.first_object); 424 VM_OBJECT_WLOCK(fs.first_object); 425 } 426 } else { 427 VM_OBJECT_WLOCK(fs.first_object); 428 } 429 430 /* 431 * Make a reference to this object to prevent its disposal while we 432 * are messing with it. Once we have the reference, the map is free 433 * to be diddled. Since objects reference their shadows (and copies), 434 * they will stay around as well. 435 * 436 * Bump the paging-in-progress count to prevent size changes (e.g. 437 * truncation operations) during I/O. This must be done after 438 * obtaining the vnode lock in order to avoid possible deadlocks. 439 */ 440 vm_object_reference_locked(fs.first_object); 441 vm_object_pip_add(fs.first_object, 1); 442 443 fs.lookup_still_valid = TRUE; 444 445 fs.first_m = NULL; 446 447 /* 448 * Search for the page at object/offset. 449 */ 450 fs.object = fs.first_object; 451 fs.pindex = fs.first_pindex; 452 while (TRUE) { 453 /* 454 * If the object is marked for imminent termination, 455 * we retry here, since the collapse pass has raced 456 * with us. Otherwise, if we see terminally dead 457 * object, return fail. 458 */ 459 if ((fs.object->flags & OBJ_DEAD) != 0) { 460 dead = fs.object->type == OBJT_DEAD; 461 unlock_and_deallocate(&fs); 462 if (dead) 463 return (KERN_PROTECTION_FAILURE); 464 pause("vmf_de", 1); 465 goto RetryFault; 466 } 467 468 /* 469 * See if page is resident 470 */ 471 fs.m = vm_page_lookup(fs.object, fs.pindex); 472 if (fs.m != NULL) { 473 /* 474 * Wait/Retry if the page is busy. We have to do this 475 * if the page is either exclusive or shared busy 476 * because the vm_pager may be using read busy for 477 * pageouts (and even pageins if it is the vnode 478 * pager), and we could end up trying to pagein and 479 * pageout the same page simultaneously. 480 * 481 * We can theoretically allow the busy case on a read 482 * fault if the page is marked valid, but since such 483 * pages are typically already pmap'd, putting that 484 * special case in might be more effort then it is 485 * worth. We cannot under any circumstances mess 486 * around with a shared busied page except, perhaps, 487 * to pmap it. 488 */ 489 if (vm_page_busied(fs.m)) { 490 /* 491 * Reference the page before unlocking and 492 * sleeping so that the page daemon is less 493 * likely to reclaim it. 494 */ 495 vm_page_aflag_set(fs.m, PGA_REFERENCED); 496 if (fs.object != fs.first_object) { 497 if (!VM_OBJECT_TRYWLOCK( 498 fs.first_object)) { 499 VM_OBJECT_WUNLOCK(fs.object); 500 VM_OBJECT_WLOCK(fs.first_object); 501 VM_OBJECT_WLOCK(fs.object); 502 } 503 vm_page_lock(fs.first_m); 504 vm_page_free(fs.first_m); 505 vm_page_unlock(fs.first_m); 506 vm_object_pip_wakeup(fs.first_object); 507 VM_OBJECT_WUNLOCK(fs.first_object); 508 fs.first_m = NULL; 509 } 510 unlock_map(&fs); 511 if (fs.m == vm_page_lookup(fs.object, 512 fs.pindex)) { 513 vm_page_sleep_if_busy(fs.m, "vmpfw"); 514 } 515 vm_object_pip_wakeup(fs.object); 516 VM_OBJECT_WUNLOCK(fs.object); 517 PCPU_INC(cnt.v_intrans); 518 vm_object_deallocate(fs.first_object); 519 goto RetryFault; 520 } 521 vm_page_lock(fs.m); 522 vm_page_remque(fs.m); 523 vm_page_unlock(fs.m); 524 525 /* 526 * Mark page busy for other processes, and the 527 * pagedaemon. If it still isn't completely valid 528 * (readable), jump to readrest, else break-out ( we 529 * found the page ). 530 */ 531 vm_page_xbusy(fs.m); 532 if (fs.m->valid != VM_PAGE_BITS_ALL) 533 goto readrest; 534 break; 535 } 536 537 /* 538 * Page is not resident. If this is the search termination 539 * or the pager might contain the page, allocate a new page. 540 * Default objects are zero-fill, there is no real pager. 541 */ 542 if (fs.object->type != OBJT_DEFAULT || 543 fs.object == fs.first_object) { 544 if (fs.pindex >= fs.object->size) { 545 unlock_and_deallocate(&fs); 546 return (KERN_PROTECTION_FAILURE); 547 } 548 549 /* 550 * Allocate a new page for this object/offset pair. 551 * 552 * Unlocked read of the p_flag is harmless. At 553 * worst, the P_KILLED might be not observed 554 * there, and allocation can fail, causing 555 * restart and new reading of the p_flag. 556 */ 557 fs.m = NULL; 558 if (!vm_page_count_severe() || P_KILLED(curproc)) { 559#if VM_NRESERVLEVEL > 0 560 if ((fs.object->flags & OBJ_COLORED) == 0) { 561 fs.object->flags |= OBJ_COLORED; 562 fs.object->pg_color = atop(vaddr) - 563 fs.pindex; 564 } 565#endif 566 alloc_req = P_KILLED(curproc) ? 567 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 568 if (fs.object->type != OBJT_VNODE && 569 fs.object->backing_object == NULL) 570 alloc_req |= VM_ALLOC_ZERO; 571 fs.m = vm_page_alloc(fs.object, fs.pindex, 572 alloc_req); 573 } 574 if (fs.m == NULL) { 575 unlock_and_deallocate(&fs); 576 VM_WAITPFAULT; 577 goto RetryFault; 578 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 579 break; 580 } 581 582readrest: 583 /* 584 * We have found a valid page or we have allocated a new page. 585 * The page thus may not be valid or may not be entirely 586 * valid. 587 * 588 * Attempt to fault-in the page if there is a chance that the 589 * pager has it, and potentially fault in additional pages 590 * at the same time. For default objects simply provide 591 * zero-filled pages. 592 */ 593 if (fs.object->type != OBJT_DEFAULT) { 594 int rv; 595 u_char behavior = vm_map_entry_behavior(fs.entry); 596 597 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 598 P_KILLED(curproc)) { 599 behind = 0; 600 ahead = 0; 601 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 602 behind = 0; 603 ahead = atop(fs.entry->end - vaddr) - 1; 604 if (ahead > VM_FAULT_READ_AHEAD_MAX) 605 ahead = VM_FAULT_READ_AHEAD_MAX; 606 if (fs.pindex == fs.entry->next_read) 607 vm_fault_cache_behind(&fs, 608 VM_FAULT_READ_MAX); 609 } else { 610 /* 611 * If this is a sequential page fault, then 612 * arithmetically increase the number of pages 613 * in the read-ahead window. Otherwise, reset 614 * the read-ahead window to its smallest size. 615 */ 616 behind = atop(vaddr - fs.entry->start); 617 if (behind > VM_FAULT_READ_BEHIND) 618 behind = VM_FAULT_READ_BEHIND; 619 ahead = atop(fs.entry->end - vaddr) - 1; 620 era = fs.entry->read_ahead; 621 if (fs.pindex == fs.entry->next_read) { 622 nera = era + behind; 623 if (nera > VM_FAULT_READ_AHEAD_MAX) 624 nera = VM_FAULT_READ_AHEAD_MAX; 625 behind = 0; 626 if (ahead > nera) 627 ahead = nera; 628 if (era == VM_FAULT_READ_AHEAD_MAX) 629 vm_fault_cache_behind(&fs, 630 VM_FAULT_CACHE_BEHIND); 631 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 632 ahead = VM_FAULT_READ_AHEAD_MIN; 633 if (era != ahead) 634 fs.entry->read_ahead = ahead; 635 } 636 637 /* 638 * Call the pager to retrieve the data, if any, after 639 * releasing the lock on the map. We hold a ref on 640 * fs.object and the pages are exclusive busied. 641 */ 642 unlock_map(&fs); 643 644 if (fs.object->type == OBJT_VNODE && 645 (vp = fs.object->handle) != fs.vp) { 646 unlock_vp(&fs); 647 locked = VOP_ISLOCKED(vp); 648 649 if (locked != LK_EXCLUSIVE) 650 locked = LK_SHARED; 651 /* Do not sleep for vnode lock while fs.m is busy */ 652 error = vget(vp, locked | LK_CANRECURSE | 653 LK_NOWAIT, curthread); 654 if (error != 0) { 655 vhold(vp); 656 release_page(&fs); 657 unlock_and_deallocate(&fs); 658 error = vget(vp, locked | LK_RETRY | 659 LK_CANRECURSE, curthread); 660 vdrop(vp); 661 fs.vp = vp; 662 KASSERT(error == 0, 663 ("vm_fault: vget failed")); 664 goto RetryFault; 665 } 666 fs.vp = vp; 667 } 668 KASSERT(fs.vp == NULL || !fs.map->system_map, 669 ("vm_fault: vnode-backed object mapped by system map")); 670 671 /* 672 * now we find out if any other pages should be paged 673 * in at this time this routine checks to see if the 674 * pages surrounding this fault reside in the same 675 * object as the page for this fault. If they do, 676 * then they are faulted in also into the object. The 677 * array "marray" returned contains an array of 678 * vm_page_t structs where one of them is the 679 * vm_page_t passed to the routine. The reqpage 680 * return value is the index into the marray for the 681 * vm_page_t passed to the routine. 682 * 683 * fs.m plus the additional pages are exclusive busied. 684 */ 685 faultcount = vm_fault_additional_pages( 686 fs.m, behind, ahead, marray, &reqpage); 687 688 rv = faultcount ? 689 vm_pager_get_pages(fs.object, marray, faultcount, 690 reqpage) : VM_PAGER_FAIL; 691 692 if (rv == VM_PAGER_OK) { 693 /* 694 * Found the page. Leave it busy while we play 695 * with it. 696 */ 697 698 /* 699 * Relookup in case pager changed page. Pager 700 * is responsible for disposition of old page 701 * if moved. 702 */ 703 fs.m = vm_page_lookup(fs.object, fs.pindex); 704 if (!fs.m) { 705 unlock_and_deallocate(&fs); 706 goto RetryFault; 707 } 708 709 hardfault++; 710 break; /* break to PAGE HAS BEEN FOUND */ 711 } 712 /* 713 * Remove the bogus page (which does not exist at this 714 * object/offset); before doing so, we must get back 715 * our object lock to preserve our invariant. 716 * 717 * Also wake up any other process that may want to bring 718 * in this page. 719 * 720 * If this is the top-level object, we must leave the 721 * busy page to prevent another process from rushing 722 * past us, and inserting the page in that object at 723 * the same time that we are. 724 */ 725 if (rv == VM_PAGER_ERROR) 726 printf("vm_fault: pager read error, pid %d (%s)\n", 727 curproc->p_pid, curproc->p_comm); 728 /* 729 * Data outside the range of the pager or an I/O error 730 */ 731 /* 732 * XXX - the check for kernel_map is a kludge to work 733 * around having the machine panic on a kernel space 734 * fault w/ I/O error. 735 */ 736 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 737 (rv == VM_PAGER_BAD)) { 738 vm_page_lock(fs.m); 739 vm_page_free(fs.m); 740 vm_page_unlock(fs.m); 741 fs.m = NULL; 742 unlock_and_deallocate(&fs); 743 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 744 } 745 if (fs.object != fs.first_object) { 746 vm_page_lock(fs.m); 747 vm_page_free(fs.m); 748 vm_page_unlock(fs.m); 749 fs.m = NULL; 750 /* 751 * XXX - we cannot just fall out at this 752 * point, m has been freed and is invalid! 753 */ 754 } 755 } 756 757 /* 758 * We get here if the object has default pager (or unwiring) 759 * or the pager doesn't have the page. 760 */ 761 if (fs.object == fs.first_object) 762 fs.first_m = fs.m; 763 764 /* 765 * Move on to the next object. Lock the next object before 766 * unlocking the current one. 767 */ 768 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 769 next_object = fs.object->backing_object; 770 if (next_object == NULL) { 771 /* 772 * If there's no object left, fill the page in the top 773 * object with zeros. 774 */ 775 if (fs.object != fs.first_object) { 776 vm_object_pip_wakeup(fs.object); 777 VM_OBJECT_WUNLOCK(fs.object); 778 779 fs.object = fs.first_object; 780 fs.pindex = fs.first_pindex; 781 fs.m = fs.first_m; 782 VM_OBJECT_WLOCK(fs.object); 783 } 784 fs.first_m = NULL; 785 786 /* 787 * Zero the page if necessary and mark it valid. 788 */ 789 if ((fs.m->flags & PG_ZERO) == 0) { 790 pmap_zero_page(fs.m); 791 } else { 792 PCPU_INC(cnt.v_ozfod); 793 } 794 PCPU_INC(cnt.v_zfod); 795 fs.m->valid = VM_PAGE_BITS_ALL; 796 /* Don't try to prefault neighboring pages. */ 797 faultcount = 1; 798 break; /* break to PAGE HAS BEEN FOUND */ 799 } else { 800 KASSERT(fs.object != next_object, 801 ("object loop %p", next_object)); 802 VM_OBJECT_WLOCK(next_object); 803 vm_object_pip_add(next_object, 1); 804 if (fs.object != fs.first_object) 805 vm_object_pip_wakeup(fs.object); 806 VM_OBJECT_WUNLOCK(fs.object); 807 fs.object = next_object; 808 } 809 } 810 811 vm_page_assert_xbusied(fs.m); 812 813 /* 814 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 815 * is held.] 816 */ 817 818 /* 819 * If the page is being written, but isn't already owned by the 820 * top-level object, we have to copy it into a new page owned by the 821 * top-level object. 822 */ 823 if (fs.object != fs.first_object) { 824 /* 825 * We only really need to copy if we want to write it. 826 */ 827 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 828 /* 829 * This allows pages to be virtually copied from a 830 * backing_object into the first_object, where the 831 * backing object has no other refs to it, and cannot 832 * gain any more refs. Instead of a bcopy, we just 833 * move the page from the backing object to the 834 * first object. Note that we must mark the page 835 * dirty in the first object so that it will go out 836 * to swap when needed. 837 */ 838 is_first_object_locked = FALSE; 839 if ( 840 /* 841 * Only one shadow object 842 */ 843 (fs.object->shadow_count == 1) && 844 /* 845 * No COW refs, except us 846 */ 847 (fs.object->ref_count == 1) && 848 /* 849 * No one else can look this object up 850 */ 851 (fs.object->handle == NULL) && 852 /* 853 * No other ways to look the object up 854 */ 855 ((fs.object->type == OBJT_DEFAULT) || 856 (fs.object->type == OBJT_SWAP)) && 857 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 858 /* 859 * We don't chase down the shadow chain 860 */ 861 fs.object == fs.first_object->backing_object) { 862 /* 863 * get rid of the unnecessary page 864 */ 865 vm_page_lock(fs.first_m); 866 vm_page_free(fs.first_m); 867 vm_page_unlock(fs.first_m); 868 /* 869 * grab the page and put it into the 870 * process'es object. The page is 871 * automatically made dirty. 872 */ 873 if (vm_page_rename(fs.m, fs.first_object, 874 fs.first_pindex)) { 875 unlock_and_deallocate(&fs); 876 goto RetryFault; 877 } 878#if VM_NRESERVLEVEL > 0 879 /* 880 * Rename the reservation. 881 */ 882 vm_reserv_rename(fs.m, fs.first_object, 883 fs.object, OFF_TO_IDX( 884 fs.first_object->backing_object_offset)); 885#endif 886 vm_page_xbusy(fs.m); 887 fs.first_m = fs.m; 888 fs.m = NULL; 889 PCPU_INC(cnt.v_cow_optim); 890 } else { 891 /* 892 * Oh, well, lets copy it. 893 */ 894 pmap_copy_page(fs.m, fs.first_m); 895 fs.first_m->valid = VM_PAGE_BITS_ALL; 896 if ((fault_flags & VM_FAULT_WIRE) == 0) { 897 prot &= ~VM_PROT_WRITE; 898 fault_type &= ~VM_PROT_WRITE; 899 } 900 if (wired && (fault_flags & 901 VM_FAULT_WIRE) == 0) { 902 vm_page_lock(fs.first_m); 903 vm_page_wire(fs.first_m); 904 vm_page_unlock(fs.first_m); 905 906 vm_page_lock(fs.m); 907 vm_page_unwire(fs.m, FALSE); 908 vm_page_unlock(fs.m); 909 } 910 /* 911 * We no longer need the old page or object. 912 */ 913 release_page(&fs); 914 } 915 /* 916 * fs.object != fs.first_object due to above 917 * conditional 918 */ 919 vm_object_pip_wakeup(fs.object); 920 VM_OBJECT_WUNLOCK(fs.object); 921 /* 922 * Only use the new page below... 923 */ 924 fs.object = fs.first_object; 925 fs.pindex = fs.first_pindex; 926 fs.m = fs.first_m; 927 if (!is_first_object_locked) 928 VM_OBJECT_WLOCK(fs.object); 929 PCPU_INC(cnt.v_cow_faults); 930 curthread->td_cow++; 931 } else { 932 prot &= ~VM_PROT_WRITE; 933 } 934 } 935 936 /* 937 * We must verify that the maps have not changed since our last 938 * lookup. 939 */ 940 if (!fs.lookup_still_valid) { 941 vm_object_t retry_object; 942 vm_pindex_t retry_pindex; 943 vm_prot_t retry_prot; 944 945 if (!vm_map_trylock_read(fs.map)) { 946 release_page(&fs); 947 unlock_and_deallocate(&fs); 948 goto RetryFault; 949 } 950 fs.lookup_still_valid = TRUE; 951 if (fs.map->timestamp != fs.map_generation) { 952 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 953 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 954 955 /* 956 * If we don't need the page any longer, put it on the inactive 957 * list (the easiest thing to do here). If no one needs it, 958 * pageout will grab it eventually. 959 */ 960 if (result != KERN_SUCCESS) { 961 release_page(&fs); 962 unlock_and_deallocate(&fs); 963 964 /* 965 * If retry of map lookup would have blocked then 966 * retry fault from start. 967 */ 968 if (result == KERN_FAILURE) 969 goto RetryFault; 970 return (result); 971 } 972 if ((retry_object != fs.first_object) || 973 (retry_pindex != fs.first_pindex)) { 974 release_page(&fs); 975 unlock_and_deallocate(&fs); 976 goto RetryFault; 977 } 978 979 /* 980 * Check whether the protection has changed or the object has 981 * been copied while we left the map unlocked. Changing from 982 * read to write permission is OK - we leave the page 983 * write-protected, and catch the write fault. Changing from 984 * write to read permission means that we can't mark the page 985 * write-enabled after all. 986 */ 987 prot &= retry_prot; 988 } 989 } 990 /* 991 * If the page was filled by a pager, update the map entry's 992 * last read offset. Since the pager does not return the 993 * actual set of pages that it read, this update is based on 994 * the requested set. Typically, the requested and actual 995 * sets are the same. 996 * 997 * XXX The following assignment modifies the map 998 * without holding a write lock on it. 999 */ 1000 if (hardfault) 1001 fs.entry->next_read = fs.pindex + faultcount - reqpage; 1002 1003 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true); 1004 vm_page_assert_xbusied(fs.m); 1005 1006 /* 1007 * Page must be completely valid or it is not fit to 1008 * map into user space. vm_pager_get_pages() ensures this. 1009 */ 1010 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 1011 ("vm_fault: page %p partially invalid", fs.m)); 1012 VM_OBJECT_WUNLOCK(fs.object); 1013 1014 /* 1015 * Put this page into the physical map. We had to do the unlock above 1016 * because pmap_enter() may sleep. We don't put the page 1017 * back on the active queue until later so that the pageout daemon 1018 * won't find it (yet). 1019 */ 1020 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1021 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1022 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1023 wired == 0) 1024 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 1025 VM_OBJECT_WLOCK(fs.object); 1026 vm_page_lock(fs.m); 1027 1028 /* 1029 * If the page is not wired down, then put it where the pageout daemon 1030 * can find it. 1031 */ 1032 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1033 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1034 vm_page_wire(fs.m); 1035 } else 1036 vm_page_activate(fs.m); 1037 if (m_hold != NULL) { 1038 *m_hold = fs.m; 1039 vm_page_hold(fs.m); 1040 } 1041 vm_page_unlock(fs.m); 1042 vm_page_xunbusy(fs.m); 1043 1044 /* 1045 * Unlock everything, and return 1046 */ 1047 unlock_and_deallocate(&fs); 1048 if (hardfault) { 1049 PCPU_INC(cnt.v_io_faults); 1050 curthread->td_ru.ru_majflt++; 1051 } else 1052 curthread->td_ru.ru_minflt++; 1053 1054 return (KERN_SUCCESS); 1055} 1056 1057/* 1058 * Speed up the reclamation of up to "distance" pages that precede the 1059 * faulting pindex within the first object of the shadow chain. 1060 */ 1061static void 1062vm_fault_cache_behind(const struct faultstate *fs, int distance) 1063{ 1064 vm_object_t first_object, object; 1065 vm_page_t m, m_prev; 1066 vm_pindex_t pindex; 1067 1068 object = fs->object; 1069 VM_OBJECT_ASSERT_WLOCKED(object); 1070 first_object = fs->first_object; 1071 if (first_object != object) { 1072 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1073 VM_OBJECT_WUNLOCK(object); 1074 VM_OBJECT_WLOCK(first_object); 1075 VM_OBJECT_WLOCK(object); 1076 } 1077 } 1078 /* Neither fictitious nor unmanaged pages can be cached. */ 1079 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1080 if (fs->first_pindex < distance) 1081 pindex = 0; 1082 else 1083 pindex = fs->first_pindex - distance; 1084 if (pindex < OFF_TO_IDX(fs->entry->offset)) 1085 pindex = OFF_TO_IDX(fs->entry->offset); 1086 m = first_object != object ? fs->first_m : fs->m; 1087 vm_page_assert_xbusied(m); 1088 m_prev = vm_page_prev(m); 1089 while ((m = m_prev) != NULL && m->pindex >= pindex && 1090 m->valid == VM_PAGE_BITS_ALL) { 1091 m_prev = vm_page_prev(m); 1092 if (vm_page_busied(m)) 1093 continue; 1094 vm_page_lock(m); 1095 if (m->hold_count == 0 && m->wire_count == 0) { 1096 pmap_remove_all(m); 1097 vm_page_aflag_clear(m, PGA_REFERENCED); 1098 if (m->dirty != 0) 1099 vm_page_deactivate(m); 1100 else 1101 vm_page_cache(m); 1102 } 1103 vm_page_unlock(m); 1104 } 1105 } 1106 if (first_object != object) 1107 VM_OBJECT_WUNLOCK(first_object); 1108} 1109 1110/* 1111 * vm_fault_prefault provides a quick way of clustering 1112 * pagefaults into a processes address space. It is a "cousin" 1113 * of vm_map_pmap_enter, except it runs at page fault time instead 1114 * of mmap time. 1115 */ 1116static void 1117vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1118 int faultcount, int reqpage) 1119{ 1120 pmap_t pmap; 1121 vm_map_entry_t entry; 1122 vm_object_t backing_object, lobject; 1123 vm_offset_t addr, starta; 1124 vm_pindex_t pindex; 1125 vm_page_t m; 1126 int backward, forward, i; 1127 1128 pmap = fs->map->pmap; 1129 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1130 return; 1131 1132 if (faultcount > 0) { 1133 backward = reqpage; 1134 forward = faultcount - reqpage - 1; 1135 } else { 1136 backward = PFBAK; 1137 forward = PFFOR; 1138 } 1139 entry = fs->entry; 1140 1141 if (addra < backward * PAGE_SIZE) { 1142 starta = entry->start; 1143 } else { 1144 starta = addra - backward * PAGE_SIZE; 1145 if (starta < entry->start) 1146 starta = entry->start; 1147 } 1148 1149 /* 1150 * Generate the sequence of virtual addresses that are candidates for 1151 * prefaulting in an outward spiral from the faulting virtual address, 1152 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1153 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1154 * If the candidate address doesn't have a backing physical page, then 1155 * the loop immediately terminates. 1156 */ 1157 for (i = 0; i < 2 * imax(backward, forward); i++) { 1158 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1159 PAGE_SIZE); 1160 if (addr > addra + forward * PAGE_SIZE) 1161 addr = 0; 1162 1163 if (addr < starta || addr >= entry->end) 1164 continue; 1165 1166 if (!pmap_is_prefaultable(pmap, addr)) 1167 continue; 1168 1169 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1170 lobject = entry->object.vm_object; 1171 VM_OBJECT_RLOCK(lobject); 1172 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1173 lobject->type == OBJT_DEFAULT && 1174 (backing_object = lobject->backing_object) != NULL) { 1175 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1176 0, ("vm_fault_prefault: unaligned object offset")); 1177 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1178 VM_OBJECT_RLOCK(backing_object); 1179 VM_OBJECT_RUNLOCK(lobject); 1180 lobject = backing_object; 1181 } 1182 if (m == NULL) { 1183 VM_OBJECT_RUNLOCK(lobject); 1184 break; 1185 } 1186 if (m->valid == VM_PAGE_BITS_ALL && 1187 (m->flags & PG_FICTITIOUS) == 0) 1188 pmap_enter_quick(pmap, addr, m, entry->protection); 1189 VM_OBJECT_RUNLOCK(lobject); 1190 } 1191} 1192 1193/* 1194 * Hold each of the physical pages that are mapped by the specified range of 1195 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1196 * and allow the specified types of access, "prot". If all of the implied 1197 * pages are successfully held, then the number of held pages is returned 1198 * together with pointers to those pages in the array "ma". However, if any 1199 * of the pages cannot be held, -1 is returned. 1200 */ 1201int 1202vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1203 vm_prot_t prot, vm_page_t *ma, int max_count) 1204{ 1205 vm_offset_t end, va; 1206 vm_page_t *mp; 1207 int count; 1208 boolean_t pmap_failed; 1209 1210 if (len == 0) 1211 return (0); 1212 end = round_page(addr + len); 1213 addr = trunc_page(addr); 1214 1215 /* 1216 * Check for illegal addresses. 1217 */ 1218 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1219 return (-1); 1220 1221 if (atop(end - addr) > max_count) 1222 panic("vm_fault_quick_hold_pages: count > max_count"); 1223 count = atop(end - addr); 1224 1225 /* 1226 * Most likely, the physical pages are resident in the pmap, so it is 1227 * faster to try pmap_extract_and_hold() first. 1228 */ 1229 pmap_failed = FALSE; 1230 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1231 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1232 if (*mp == NULL) 1233 pmap_failed = TRUE; 1234 else if ((prot & VM_PROT_WRITE) != 0 && 1235 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1236 /* 1237 * Explicitly dirty the physical page. Otherwise, the 1238 * caller's changes may go unnoticed because they are 1239 * performed through an unmanaged mapping or by a DMA 1240 * operation. 1241 * 1242 * The object lock is not held here. 1243 * See vm_page_clear_dirty_mask(). 1244 */ 1245 vm_page_dirty(*mp); 1246 } 1247 } 1248 if (pmap_failed) { 1249 /* 1250 * One or more pages could not be held by the pmap. Either no 1251 * page was mapped at the specified virtual address or that 1252 * mapping had insufficient permissions. Attempt to fault in 1253 * and hold these pages. 1254 */ 1255 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1256 if (*mp == NULL && vm_fault_hold(map, va, prot, 1257 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1258 goto error; 1259 } 1260 return (count); 1261error: 1262 for (mp = ma; mp < ma + count; mp++) 1263 if (*mp != NULL) { 1264 vm_page_lock(*mp); 1265 vm_page_unhold(*mp); 1266 vm_page_unlock(*mp); 1267 } 1268 return (-1); 1269} 1270 1271/* 1272 * Routine: 1273 * vm_fault_copy_entry 1274 * Function: 1275 * Create new shadow object backing dst_entry with private copy of 1276 * all underlying pages. When src_entry is equal to dst_entry, 1277 * function implements COW for wired-down map entry. Otherwise, 1278 * it forks wired entry into dst_map. 1279 * 1280 * In/out conditions: 1281 * The source and destination maps must be locked for write. 1282 * The source map entry must be wired down (or be a sharing map 1283 * entry corresponding to a main map entry that is wired down). 1284 */ 1285void 1286vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1287 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1288 vm_ooffset_t *fork_charge) 1289{ 1290 vm_object_t backing_object, dst_object, object, src_object; 1291 vm_pindex_t dst_pindex, pindex, src_pindex; 1292 vm_prot_t access, prot; 1293 vm_offset_t vaddr; 1294 vm_page_t dst_m; 1295 vm_page_t src_m; 1296 boolean_t upgrade; 1297 1298#ifdef lint 1299 src_map++; 1300#endif /* lint */ 1301 1302 upgrade = src_entry == dst_entry; 1303 access = prot = dst_entry->protection; 1304 1305 src_object = src_entry->object.vm_object; 1306 src_pindex = OFF_TO_IDX(src_entry->offset); 1307 1308 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1309 dst_object = src_object; 1310 vm_object_reference(dst_object); 1311 } else { 1312 /* 1313 * Create the top-level object for the destination entry. (Doesn't 1314 * actually shadow anything - we copy the pages directly.) 1315 */ 1316 dst_object = vm_object_allocate(OBJT_DEFAULT, 1317 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1318#if VM_NRESERVLEVEL > 0 1319 dst_object->flags |= OBJ_COLORED; 1320 dst_object->pg_color = atop(dst_entry->start); 1321#endif 1322 } 1323 1324 VM_OBJECT_WLOCK(dst_object); 1325 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1326 ("vm_fault_copy_entry: vm_object not NULL")); 1327 if (src_object != dst_object) { 1328 dst_entry->object.vm_object = dst_object; 1329 dst_entry->offset = 0; 1330 dst_object->charge = dst_entry->end - dst_entry->start; 1331 } 1332 if (fork_charge != NULL) { 1333 KASSERT(dst_entry->cred == NULL, 1334 ("vm_fault_copy_entry: leaked swp charge")); 1335 dst_object->cred = curthread->td_ucred; 1336 crhold(dst_object->cred); 1337 *fork_charge += dst_object->charge; 1338 } else if (dst_object->cred == NULL) { 1339 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1340 dst_entry)); 1341 dst_object->cred = dst_entry->cred; 1342 dst_entry->cred = NULL; 1343 } 1344 1345 /* 1346 * If not an upgrade, then enter the mappings in the pmap as 1347 * read and/or execute accesses. Otherwise, enter them as 1348 * write accesses. 1349 * 1350 * A writeable large page mapping is only created if all of 1351 * the constituent small page mappings are modified. Marking 1352 * PTEs as modified on inception allows promotion to happen 1353 * without taking potentially large number of soft faults. 1354 */ 1355 if (!upgrade) 1356 access &= ~VM_PROT_WRITE; 1357 1358 /* 1359 * Loop through all of the virtual pages within the entry's 1360 * range, copying each page from the source object to the 1361 * destination object. Since the source is wired, those pages 1362 * must exist. In contrast, the destination is pageable. 1363 * Since the destination object does share any backing storage 1364 * with the source object, all of its pages must be dirtied, 1365 * regardless of whether they can be written. 1366 */ 1367 for (vaddr = dst_entry->start, dst_pindex = 0; 1368 vaddr < dst_entry->end; 1369 vaddr += PAGE_SIZE, dst_pindex++) { 1370again: 1371 /* 1372 * Find the page in the source object, and copy it in. 1373 * Because the source is wired down, the page will be 1374 * in memory. 1375 */ 1376 if (src_object != dst_object) 1377 VM_OBJECT_RLOCK(src_object); 1378 object = src_object; 1379 pindex = src_pindex + dst_pindex; 1380 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1381 (backing_object = object->backing_object) != NULL) { 1382 /* 1383 * Unless the source mapping is read-only or 1384 * it is presently being upgraded from 1385 * read-only, the first object in the shadow 1386 * chain should provide all of the pages. In 1387 * other words, this loop body should never be 1388 * executed when the source mapping is already 1389 * read/write. 1390 */ 1391 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1392 upgrade, 1393 ("vm_fault_copy_entry: main object missing page")); 1394 1395 VM_OBJECT_RLOCK(backing_object); 1396 pindex += OFF_TO_IDX(object->backing_object_offset); 1397 if (object != dst_object) 1398 VM_OBJECT_RUNLOCK(object); 1399 object = backing_object; 1400 } 1401 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1402 1403 if (object != dst_object) { 1404 /* 1405 * Allocate a page in the destination object. 1406 */ 1407 dst_m = vm_page_alloc(dst_object, (src_object == 1408 dst_object ? src_pindex : 0) + dst_pindex, 1409 VM_ALLOC_NORMAL); 1410 if (dst_m == NULL) { 1411 VM_OBJECT_WUNLOCK(dst_object); 1412 VM_OBJECT_RUNLOCK(object); 1413 VM_WAIT; 1414 VM_OBJECT_WLOCK(dst_object); 1415 goto again; 1416 } 1417 pmap_copy_page(src_m, dst_m); 1418 VM_OBJECT_RUNLOCK(object); 1419 dst_m->valid = VM_PAGE_BITS_ALL; 1420 dst_m->dirty = VM_PAGE_BITS_ALL; 1421 } else { 1422 dst_m = src_m; 1423 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1424 goto again; 1425 vm_page_xbusy(dst_m); 1426 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1427 ("invalid dst page %p", dst_m)); 1428 } 1429 VM_OBJECT_WUNLOCK(dst_object); 1430 1431 /* 1432 * Enter it in the pmap. If a wired, copy-on-write 1433 * mapping is being replaced by a write-enabled 1434 * mapping, then wire that new mapping. 1435 */ 1436 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1437 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1438 1439 /* 1440 * Mark it no longer busy, and put it on the active list. 1441 */ 1442 VM_OBJECT_WLOCK(dst_object); 1443 1444 if (upgrade) { 1445 if (src_m != dst_m) { 1446 vm_page_lock(src_m); 1447 vm_page_unwire(src_m, 0); 1448 vm_page_unlock(src_m); 1449 vm_page_lock(dst_m); 1450 vm_page_wire(dst_m); 1451 vm_page_unlock(dst_m); 1452 } else { 1453 KASSERT(dst_m->wire_count > 0, 1454 ("dst_m %p is not wired", dst_m)); 1455 } 1456 } else { 1457 vm_page_lock(dst_m); 1458 vm_page_activate(dst_m); 1459 vm_page_unlock(dst_m); 1460 } 1461 vm_page_xunbusy(dst_m); 1462 } 1463 VM_OBJECT_WUNLOCK(dst_object); 1464 if (upgrade) { 1465 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1466 vm_object_deallocate(src_object); 1467 } 1468} 1469 1470 1471/* 1472 * This routine checks around the requested page for other pages that 1473 * might be able to be faulted in. This routine brackets the viable 1474 * pages for the pages to be paged in. 1475 * 1476 * Inputs: 1477 * m, rbehind, rahead 1478 * 1479 * Outputs: 1480 * marray (array of vm_page_t), reqpage (index of requested page) 1481 * 1482 * Return value: 1483 * number of pages in marray 1484 */ 1485static int 1486vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1487 vm_page_t m; 1488 int rbehind; 1489 int rahead; 1490 vm_page_t *marray; 1491 int *reqpage; 1492{ 1493 int i,j; 1494 vm_object_t object; 1495 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1496 vm_page_t rtm; 1497 int cbehind, cahead; 1498 1499 VM_OBJECT_ASSERT_WLOCKED(m->object); 1500 1501 object = m->object; 1502 pindex = m->pindex; 1503 cbehind = cahead = 0; 1504 1505 /* 1506 * if the requested page is not available, then give up now 1507 */ 1508 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1509 return 0; 1510 } 1511 1512 if ((cbehind == 0) && (cahead == 0)) { 1513 *reqpage = 0; 1514 marray[0] = m; 1515 return 1; 1516 } 1517 1518 if (rahead > cahead) { 1519 rahead = cahead; 1520 } 1521 1522 if (rbehind > cbehind) { 1523 rbehind = cbehind; 1524 } 1525 1526 /* 1527 * scan backward for the read behind pages -- in memory 1528 */ 1529 if (pindex > 0) { 1530 if (rbehind > pindex) { 1531 rbehind = pindex; 1532 startpindex = 0; 1533 } else { 1534 startpindex = pindex - rbehind; 1535 } 1536 1537 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1538 rtm->pindex >= startpindex) 1539 startpindex = rtm->pindex + 1; 1540 1541 /* tpindex is unsigned; beware of numeric underflow. */ 1542 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1543 tpindex < pindex; i++, tpindex--) { 1544 1545 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1546 VM_ALLOC_IFNOTCACHED); 1547 if (rtm == NULL) { 1548 /* 1549 * Shift the allocated pages to the 1550 * beginning of the array. 1551 */ 1552 for (j = 0; j < i; j++) { 1553 marray[j] = marray[j + tpindex + 1 - 1554 startpindex]; 1555 } 1556 break; 1557 } 1558 1559 marray[tpindex - startpindex] = rtm; 1560 } 1561 } else { 1562 startpindex = 0; 1563 i = 0; 1564 } 1565 1566 marray[i] = m; 1567 /* page offset of the required page */ 1568 *reqpage = i; 1569 1570 tpindex = pindex + 1; 1571 i++; 1572 1573 /* 1574 * scan forward for the read ahead pages 1575 */ 1576 endpindex = tpindex + rahead; 1577 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1578 endpindex = rtm->pindex; 1579 if (endpindex > object->size) 1580 endpindex = object->size; 1581 1582 for (; tpindex < endpindex; i++, tpindex++) { 1583 1584 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1585 VM_ALLOC_IFNOTCACHED); 1586 if (rtm == NULL) { 1587 break; 1588 } 1589 1590 marray[i] = rtm; 1591 } 1592 1593 /* return number of pages */ 1594 return i; 1595} 1596 1597/* 1598 * Block entry into the machine-independent layer's page fault handler by 1599 * the calling thread. Subsequent calls to vm_fault() by that thread will 1600 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1601 * spurious page faults. 1602 */ 1603int 1604vm_fault_disable_pagefaults(void) 1605{ 1606 1607 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1608} 1609 1610void 1611vm_fault_enable_pagefaults(int save) 1612{ 1613 1614 curthread_pflags_restore(save); 1615} 1616